The exploration and production of hydrocarbons from subsurface formations include systems and methods for extracting the hydrocarbons from the formation. A drilling rig may be positioned on land or a body of water to support a drill string extending down into a wellbore. The drill string may include a bottom hole assembly made up of a drill bit and sensors, as well as a telemetry system capable of receiving and transmitting sensor data. Sensors disposed in the bottom hole assembly may include pressure and temperature sensors. A surface telemetry system is included for receiving telemetry data from the bottom hole assembly sensors and for transmitting commands and data to the bottom hole assembly.
Fluid “drilling mud” is pumped from the drilling platform, through the drill string, and to a drill bit supported at the lower or distal end of the drill string. The drilling mud lubricates the drill bit and carries away well cuttings generated by the drill bit as it digs deeper. The cuttings are carried in a return flow stream of drilling mud through the well annulus and back to the well drilling platform at the earth's surface. When the drilling mud reaches the platform, it is contaminated with small pieces of shale and rock that are known in the industry as well cuttings or drill cuttings. Once the drill cuttings, drilling mud, and other waste reach the platform, separation equipment is used to remove the drill cuttings from the drilling mud, so that the drilling mud may be reused.
A fluid back pressure system may be connected to a fluid discharge conduit to selectively control fluid discharge to maintain a selected pressure at the bottom of the borehole. Fluid may be pumped down the drilling fluid return system to maintain annulus pressure during times when the mud pumps are turned off. A pressure monitoring system may also be used to monitor detected borehole pressures, model expected borehole pressures for further drilling, and to control the fluid backpressure system.